博世——汽车毫米波雷达状态及趋势

AutomotiveRadar–StatusandTrendsMartinSchneiderRobertBoschGmbH,CorporateResearch,PObox777777,D-31132Hildesheim,Germany,[phone],[e-mail]—Thepapergivesabriefoverviewofautomo-tiveradar.Thestatusofthefrequencyregulationforshortandlongrangeradarissummarizedbecauseofitsimpor-tanceforcarmanufacturersandtheirsensorsuppliers.Frontendconceptsandantennatechniquesof24GHzand77GHzsensorsarebrieflydescribed.Theirimpactonthesensor’sfieldofviewandontheangularmeasurementcapabilityisdiscussed.Esp.digitalbeamformingconceptsareconsideredandpromisingresultsarepresented.I.INTRODUCTIONFirstexperimentsinthefieldofautomotiveradartookplacealreadyinthelate50’s.Inthe70’s,moreorlessintensiveradardevelopmentsstartedatmicrowavefre-quencies.Theactivitiesofthelastdecadeswereconcen-tratedmainlyondevelopmentsat17GHz,24GHz,35GHz,49GHz,60GHz,and77GHz.Evenfromtheearlybeginninginautomotiveradarthekeydriverofalltheseinvestigationshasbeentheideaofcollisionavoidance;thisideahasspentenormousmotivationformanyengi-neersallovertheworldtodevelopsmartvehicularradarunits.Duringthisquitelongperiodalotofknow-howhasbeengainedinthefieldofmicrowavesandinradarsignalprocessing.Accompaniedbytheremarkablepro-gressinsemiconductormicrowavesources(esp.GunnsourcesandGaAsMMICs)andinavailablecomputingpowerofmicrocontrollersanddigitalsignalprocessingunits,thecommercializationofautomotiveradarbecamefeasibleinthe90’s.Competingandcomplementingtechnologiesinvehicu-larsurroundsensingandsurveillanceareLidar,ultrason-ics,andvideocameras(basedonCCDorCMOSchipsincludingnear-infraredsensitivity).Carmanufacturersandsuppliersaredevelopingoptimizedsensorconfigura-tionsforcomfortandsafetyfunctionswrt.functionality,robustness,reliability,dependenceonadverseweatherconditionsetc.Lastbutnotleastthetotalsystemcostshavetomeetthemarketingtargetstobeattractivefortheendcustomers.Firstapplicationswithsurroundsensingtechnologieswereparkingaid(basedonultrasonics),collisionwarning,andAdaptiveCruiseControl(ACC).Forinstance,collisionwarningsystemsweresuccessfullyintroducedintheUSinthe90’s.Greyhoundinstalledmorethan1600radarsystems(24GHz)intheirbuslinesyieldingareductionofaccidentsof21percentin1993comparedtotheyearbefore.ACCwascommercializedforthefirsttimeinJapanin1995.WhereasLidar-ACChasbeenfavoredesp.inJa-pan,EuropeanandUScompanieshavebeenfocusedmainlyonradarbasedACC.In1999,Mercedesintro-ducedthe77GHz“Distronic”intotheSclass,followedbyotherpremiummodelsequippedoptionallywithanACC,suchasBMW7series,Jaguar(XKR,XK6),Cadil-lac(STS,XLR),AudiA8,andVWPhaeton.ACCisalsoavailableinMercedesE,CL,CLK,SLclass,BMW5and6series,AudiA6,Nissan(Cima,Primera),Toyota(Harrier,Celsior),Lexus(LS,GS),andHonda(Accord,Inspire,Odyssey).Furthermore,ACCwillbecomeanoptioninthenewBMW3seriesandinthenewVWPassat,bothwithstartofproductionin2005.WhereasEuropeancarmanufacturersoffer77GHzsystemsonlyforACCsystemssofar,theirJapanesecompetitorsHondaandToyotaalreadyintroducedanactivebrakeassistforcollisionmitigation(additionallytoACC)in2003basedon77GHzlongrangeradar(LRR)technology.IncontrasttotheonlysmoothdecelerationcapabilityofanACCsystem(becauseACCisonlymar-ketedasacomfortfeature),theactivebrakeassistpro-videsmuchhigherbrakingforcesfordeceleration,whenathreateningsituationisidentifiedandthedriverstartsbraking,butmaybenotasstrongasitwouldbenecessarytoavoidacrash.Thisshowsthetrendfrom“comfortonly”functionstoactivesafetysystemswithradarsensingtechnologiesthatserveboththecomfortandthesafetydomain.Withinthenextfewyearstheseactivesafetysystemswillbeintro-ducedinEurope.Mercedesstartedwiththefirstgenera-tionoftheirPresafesystemintheSclassin2003,whichisn’tbasedonsurroundsensingtechniquesyetbut(only)onthedataoftheelectronicstabilityprogram(ESP)andtheantilockbrakingsystem(ABS).Ifthesecontrolunitsidentifyanimminentaccidentduetothecar’sdynamics,electronicseatbelttensionerswillbeactivated,seatori-entationswillbeadapted,andthesunroofwillbeclosed.Thenextstepinthisevolutionaryprocesswillbetogainsomemoremillisecondsinadvanceforreactionandforautomaticactivationofsuitableprotectionmeasures.Boschnamesthissystem“PredictiveSafetySystem(PSS)”,whichwillhavemainlythreestages.Thefirstone(PSS1,tobeintroducedin2005)isapresetofthebrakesystem.Assoonasathreatwillbeidentifiedbythe77GHzLRR,thebrakesystemwillbepre-filled,butthiswon’tbenoticedbythedriver.Butwhenthedriverpushesthebrakepedalinsuchasituation,maximumbrakingforceswillbeavailablewithoutanylatency.Inthesecondstage(PSS2,2006)thedriverwillbenotifiedinahazardoussituationwithanautomatic,veryshortbutintensivebrakeactivation,accompaniedbyopticaloracousticsignals.Inthethirdstage(PSS3)anautomaticemergencybrakewillbeinitiatedifotherwiseacrashcouldn’tbeavoided.BoschwasrecentlyawardedforitsPSSwiththe“GelberEngel(YellowAngel)”fromthe144GeMiC2005GermanautoclubADAC(similartoAAAintheUS)inthecategory“Innovation”.Shortrangeradar(SRR)sensorsforpassengercarswillbemountedfirstinpremiumclassmodelsforpre-crashsensing,ACCsupport,parkingassistance,andblindspotsurveillance.Preferredmicrowavetechnologyis24GHzi